Two examples of phase portrait of system (3.1), (3.2) depending on the function f(v) = 1− h(v)∕p(v). It can have six (left) or four (right) stationary points. The trajectory with the initial condition (v₀, c₀ ) and sufficiently small viral load v₀ can go either to the stationary point with complete virus elimination (right) or to a weak persistent infection (left). If the initial viral load is sufficiently large, then the trajectory approaches the stationary point with large v and small c. It corresponds to a strong chronic infection or to death. Reprinted from [2].